Sharing a collection with a Community in Edelweiss is really simple. (*Publisher users see note at bottom of page!)
Go to the Catalog tab of your account. On the left side of the page, you will see Catalog Options. Click on My Collections to view your collections. Choose a collection to share and click the Share Collection icon located on the bottom right corner of the collection:
In the resulting window, check the box next to Communities and click on the ellipses to the right:
A new window will open up which will display the Communities that you have joined. Check the boxes next to each Community you wish to share your collection with and click Continue. To de-select the Community, check the box again:
You will be taken back to the previous window. Click the save icon on the bottom right corner of the window and your collection has been shared!
*Note that publisher users share collections in a different and more formal way, sharing them just like they share Markups. Details specific to publisher users and Collection Sharing can be found here.